John Henry Denig (September 8, 1838 – December 10, 1876) was a United States Marine Corps sergeant serving aboard the USS Brooklyn during the American Civil War.

He enlisted in Marine Corps from Philadelphia in June 1861 and served as a sergeant on the USS Brooklyn during the Battle of Mobile Bay, Alabama.

[1] Mobile was the last Confederate-held port on the Gulf of Mexico east of the Mississippi River, and its capture would complete the Union blockade in the area.

[3] Denig died of health complications at age 38 and was buried in York's Prospect Hill Cemetery.

Denig fought his gun with skill and courage throughout the furious 2-hour battle which resulted in the surrender of the rebel ram Tennessee and in the damaging and destruction of batteries at Fort Morgan.